Bit grinding jig



Sept. 24, 1940. R R FRANC@ 2,215,694

BIT GRINDING JIG Filed May 4, 1938 INVENTOR h@ R 7kg/cfs. RNEY l Patented Sept. 24, 1940 UNITED STATES BIT GRINDING JIG Paul R.. Francis, Los Angeles, Calif., assigner to Alloy Steel & Metals Company, Los Angeles, Calif., a corporation of California Application May 4, 1938, Serial No. 205,964

4 Claims.

This invention relates to a bit grinding jig, particularly useful in the grinding and sharpenlng of detachable rock drill bits of the type used in mining, quarrying and the like.

An object of my invention is to provide a bit grinding jig of the character stated, which is rapid, accurate and dependable in operation.

Another object is to provide a jig of the character stated which will sharpen bits of all makes 10 and sizes.

A feature of my invention is to provide a jig which will grind both the cutting edges and the gauge of the bit.

A further feature is to provide a jig which can lu be easily mounted on a bench adjacent to any well known type of grinding wheel equipment, the standard type of wheel being sunicient to sharpen the bits; that is, the wheel need not be of any special form.

Other objects, advantages and features of invention may appear from the accompanying drawing, the subjoined detailed description and the appended claims.

In the drawing:

Figure 1 is an end view of the grinding jig in position adjacent the grinding wheel.

Figure 2 is a plan View of the same.

Figure 3 is a plan View similar to Figure 2, showing the bit in gauge grinding position.

Figure 4 is a side View of the mandrel guide socket.

Figure 5 is a bottom plan view of the bit mandrel guide.

Figure 6 is a side elevation of the bit mandrel 35 guide.

Referring more particularly to the drawing, the bit grinding jig I is mounted on a bench or table adjacent the grinding wheel 2, which wheel is mounted on the usual arbor 3, rotated by a 0 suitable source of power not shown. The grinding wheel 2 is the usual and well known flat face type, and it will be noted that no special form of wheel is required to grind the bits when my jig is employed. The .iig consists of a bed plate 4 15 which is bolted to the bench or table adjacent the grinding wheel 2 by means of bolts 5-5. A slide head 6 is mounted on the bed plate 4 and this head is adapted to be moved at right angles to the center line of the arbor 3. The slide head 0 is provided with an elongated slot 1, through which a clamp screw or stud bolt extends, and a clamp nut 8 screws onto the bolt or stud, thus holding the slide head in proper relation to the grinding wheel.

55 A pair of sockets 9, I0 are integrally formed on the inner end of the slide 6, the center lines of these sockets are inclined downwardly and inwardly for purpose to be further described. For the purpose of grinding the cutting faces Il of the bit I2, the bit is mounted as shown in Figures 5 1 and 2; a bit mandrel guide I3 is positioned in either of the sockets 9 or I9. The mandrel guide is a T shaped iitting and includes a post i9, which fits into either of the sockets 9 or IU. The sockets 9, I0 are each provided with notches l5 10 to receive the depending lug I6 on the lower part of the guide I3, thus the guide is non-rotatably held in the sockets. The bit I2 is attached to the outer end of a mandrel I1 and a handle I8 is attached to the mandrel for the purpose of holding the bit against the grinding wheel 2.

The various cutting faces of the bit I2 are presented to the grinding wheel 2 by releasing the set screw 8 and sliding the head 6 back, and then again advancing the head so that the bit engages 20 the face of the grinding wheel, or by slidingthe mandrel Il in the guide I3.

For the purpose of grinding the gauge angle on the bits, the jig is used as shown in Figure 3. This consists of a slide head I9, which is slidably 25 mounted on the bed plate 4, a stud extends through the slot 2|] and a clamp screw 2| screws onto the stud and against the head I9, thus holding the head in proper position relative to the grinding wheel 2. The head I9 is provided with a vertical socket 22, into which a set screw 23 extends. A mandrel guide socket 24 is adapted to t into the socket 22 and is held in position by the set screw 23. The post I4 of the mandrel guide I3'then nts into the socket 24, of the gauge, thus the bit is ground as shown in Figure 3. The lugs I6 rit into the grooves 25 when the gauge grinding operation is in progress. The bit mandrel guide I3 is thus non-rotatably held in the socket 24 so that the bit will be held at a proper angle to the face of the grinding wheel 2; the bit mandrel Il can be rotated by the handle I8 so that the various blades of the bit can be carried against the face of the grinding wheel. The handle I8 provides a convenient hand hold for the workmen while grinding the bit, as well as affording means of rotating the bit to various positions so that the cutting faces as well as the gauge can be ground.

Having described my invention, I claim:

l. A bit mandrel guide comprising a base, a pair of heads adjustably mounted on the base, said heads being substantially parallel, a pair of spaced sockets arranged on one of the heads, said sockets being inclined to the plane of the base, a u.

bit mandrel guide being adapted to fit into either of the sockets, a mandrel on which a bit is mounted, said mandrel extending through the mandrel guide, a socket on the other head, an adapter iitting into the last named socket, means adjustably mounting the adapter in the last named socket, said mandrel guide fitting into the adapter when the gauge of the bit is ground.

2. A bit mandrel guide comprising a base, a pair of heads adjustably mounted on the base, said heads being substantially parallel, a pair of spaced sockets arranged on one of the heads, said sockets being inclined to the plane of the base, a, mandrel guide being adapted to it into either of the sockets, a mandrel on which a bit is mounted, said mandrel extending through the mandrel guide, a socket on the other head, an adapter fitting into the last named socket, means adjustably mounting the adapter in the last named socket, said mandrel guide fitting into the adapter when the gauge of the bit is ground, and means nonrotatably holding the mandrel guide in the sockets.

3. A bit mandrel guide comprising a base, a pair of heads adjustably mounted on the base, said heads being substantially parallel, a pair of spaced sockets on one of the heads, said sockets being inclined downwardly and inwardly, a bit mandrel guide adapted to fit into either of the sockets, means rotatably holding the mandrel guide in the sockets, a mandrel on which a bit is mounted, said mandrel extending through the mandrel guide, a handle on the outer end of the mandrel, a vertical socket on the second head, an adapter tting in the last named socket, a set screw in the socket bearing against the adapter, the mandrel guide being adapted to t into the adapter, the means non-rotatably holding the mandrel guide in the adapter.

4. A bit grinding jig for bits having teeth, which are V-shaped in cross-section, the teeth being radially arranged on the bit, comprising a base, a head mounted on the base, a pair of sockets rising from the head, said sockets being arranged at an angle to the plane of the base, a bit mandrel guide removably mounted in a socket, a mandrel on which the bit is mounted, said mandrel extending through the mandrel guide and means non-rotatably holding the mandrel guide in a socket, a second head mounted on the base, a socket on the second head, an adapter tting into the last-named socket, means adjustably mounting the adapter in the last-named socket, said mandrel guide fitting into the adapter when the gauge of the bit is ground.

PAUL R. FRANCIS. 

